1. Field of the Invention
The present invention relates to a method for manufacturing a magnetic head for recording on a recording medium comprising a hard film, such as a disk, by applying a magnetic field thereto. Particularly, the present invention relates to a method for manufacturing a magnetic head capable of precisely forming component members.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 11-232609 discloses a process for manufacturing a magnetic head. FIG. 2 of this document shows a step for manufacturing the magnetic head in which an alumina film for forming a gap is formed on a substrate to protrude therefrom, and then a permalloy film is formed over the alumina film (FIG. 2A), and a SiO2 film is further formed on the permalloy film (FIG. 2B).
FIG. 18 shows the state shown in FIG. 2B of Japanese Unexamined Patent Application Publication No. 11-232609. As shown in FIG. 18, an alumina film 2 is formed on a substrate 1 to protrude therefrom, and a permalloy film 3 formed over the alumina film 2 rises in the vicinity of the top of the alumina film 2 to form a protruding portion 3a. The permalloy film 3 also has a flat portion 3b formed around the protruding portion 3b. 
Therefore, a SiO4 film 4 formed on the permalloy film 3 also has a flat portion 4b formed on the flat portion 3b of the permalloy film 3, and a protruding portion 4a formed on the protruding portion 3a so as to protrude above the upper surface 4b1 of the flat portion 4b, depending upon the shape of the permalloy film 3.
According to the process disclosed in this document, in the state shown in FIG. 18 (FIG. 2B of this document), the upper surface of the SiO2 film 4 is polished by CMP (Chemical Mechanical Polishing) to cut the protruding portions 4a and 3a. In this step, the SiO2 film 4 has a stopper function to stop the polishing at the upper surface 4b1 of the flat portion 4b and to form the upper surfaces of the SiO2 film 4, the permalloy film 3, and the alumina film 2 as the same planarized surface. FIG. 19 shows the state at the end of polishing, which is shown in FIG. 2C of the document.
Japanese Unexamined Patent Application Publication No. 7-272211 also discloses a process for manufacturing a magnetic head on the basis of the same idea as that of the invention disclosed in the above-described document. FIG. 1 of this document shows a step for manufacturing the magnetic head in which a magnetic core is formed on a substrate with a first insulating layer provided therebetween, a second insulating layer is formed to cover the sides and upper surface of the magnetic core, and a hard metal film functioning as a polishing stopper layer is formed on the second insulating layer (FIG. 1A).
FIG. 20 shows the state shown in FIG. 1A of this document. As shown in FIG. 20, a first insulating film 12 is formed on a substrate 11, and a magnetic core 13 is formed on the first insulating film 12 so as to protrude therefrom. Furthermore, a second insulating film 14 formed over the magnetic core 13 rises in the vicinity of the top of the magnetic core 13 to form a protruding portion 14a. The second insulating layer 14 also has a flat portion 14b around the protruding portion 14a. Therefore, the hard metal film 15 formed on the second insulating film 14 also has a flat portion 15b formed on the flat portion 14b of the second insulating film 14, and a protruding portion 15a formed on the protruding portion 14a so as to protrude above the upper surface 15b1 of the flat portion 15b, depending upon the shape of the second insulating film 14.
According to the process disclosed in the document, in the state shown in FIG. 20 (FIG. 1A of the document), the upper surface of the hard metal film 15 is polished using a polishing pad comprising an elastic material to cut the protruding portions 15a and 14a. In this step, the hard metal film 15 functions as a stopper to stop polishing at the upper surface 15b1 of the flat portion 15b, thereby forming the upper surfaces of the hard metal film 15 and the magnetic core 13 as the same planarized surface. The state at the end of polishing is shown in FIG. 1D of the document. FIG. 21 shows the state shown in FIG. 2C of the document.
However, in the invention disclosed in Japanese Unexamined Patent Application Publication No. 11-232609, when the protruding portions 4a and 3a are polished by CMP, a difference between the CMP rates or etching rates of the SiO2 film 4 forming the protruding portion 4a and the permalloy film 3 forming the protruding portion 3a causes the following problem:
In the process for manufacturing the magnetic head disclosed in Japanese Unexamined Patent Application Publication No. 11-232609, as shown in FIG. 18, the SiO2 film 4 has the protruding portion 4a protruding above the upper surface 4b1 of the flat portion 4b. Therefore, during the time from the start of polishing shown in FIG. 18 to the end of polishing shown in FIG. 19, there is a state in which both the protruding portion 3a and the protruding portion 4a formed thereon are simultaneously polished as shown by line D—D in FIG. 18.
In the state in which both the protruding portion 3a and the protruding portion 4a formed thereon are simultaneously polished, when the CMP rate or etching rate of the permalloy film 3 forming the protruding portion 3a is higher than that of the SiO2 film 4 forming the protruding portion 4a, the permalloy film 3 is more rapidly polished than the SiO2 film 4. Thus, when the SiO2 film 4 is polished to the upper surface 4b1 of the flat portion 4b of the SiO2 film 4, the permalloy film 3 is excessively polished to a position lower than the upper surface 4b1 of the flat portion 4b, thereby failing to form the planarized surface. When the planarized surface cannot be formed, the thickness of the alumina film 2, which functions as a read-write gap, cannot be controlled, and thus the magnetic head cannot be precisely manufactured.
Conversely, when the CMP rate or etching rate of the permalloy film 3 forming the protruding portion 3a is lower than that of the SiO2 film 4 forming the protruding portion 4a, the permalloy film 3 is more slowly polished than the SiO2 film 4. Thus, when the SiO2 film 4 is polished to the upper surface 4b1 of the flat portion 4b of the SiO2 film 4, the permalloy film 3 is polished to a position above the upper surface 4b1 of the flat portion 4b, thereby failing to form the planarized surface. Therefore, the magnetic head cannot be precisely manufactured.
On the other hand, even in the invention disclosed in Japanese Unexamined Patent Application Publication No. 7-272211, as shown in FIG. 20, the hard metal film 15 has the protruding portion 15a formed to protrude above the upper surface 15b1 of the flat portion 15b. There is thus a state in which both the protruding portion 14a and the protruding portion 15a formed thereon are simultaneously polished as shown by line D—D in FIG. 20. Therefore, when the CMP rate or etching rate of the second insulating film 14 is different from that of the hard metal film 15, the planarized surface cannot be formed at the end of polishing to the upper surface 15b1 of the flat portion 15b of the hard metal film 15, like in the invention disclosed in Japanese Unexamined Patent Application Publication No. 11-232609. Therefore, the magnetic head cannot be precisely manufactured.